Environment Canterbury (ECan) is investigating claims South Canterbury farmers gamed water flow meters on the Pareora River to evade irrigation restrictions.

An ECan spokeswoman confirmed yesterday the regional authority would investigate Pareora hut owners' reports of men building a weir next to a water gauge on the river.

Witnesses, who did not want to be named, said they saw three "mature men" jump off a flat deck ute with shovels in hand and dig about in the Pareora River about 11.45am on Saturday.

The hut owners took little notice until they found a weir blocking part of the river where the men had been digging.

The newly created dam was next to a water reader gauge. The hut owners suspected the men, whom they identified as local farmers, were trying to artificially raise recorded water flows to avoid irrigation restrictions.

The witnesses checked their theory by destroying part of the weir and saw the water level drop 100 millimetres immediately. Removing more rocks later made the water level fall by another 100mm.

...which meant that these farmers got to keep on irrigating. It was a deliberate effort to evade the restrictions on their irrigation consents and steal water from the public. In other words, fraud - and it should be prosecuted as such.